1. Field of the Invention
The present invention relates to a field emission device (FED) which is capable of focusing an electron beam on an anode, and ensures stable operation with high anode voltages, and a method for fabricating the FED.
2. Description of the Related Art
An FED panel with a conventional FED is illustrated in FIG. 1. A cathode 2 is formed over a substrate 1 with a metal such as chromium (Cr), and a resistor layer 3 is formed over the cathode 2 with an amorphous silicon. A gate insulation layer 4 with a well 4a, through which the bottom of the resistor layer 3 is exposed, is formed on the resistor layer 3 with an insulation material such as SiO2. A micro-tip 5 formed of a metal such as molybdenum (Mo) is located in the well 4a. A gate electrode 6 with a gate 6a aligned with the well 4a is formed on the gate insulation layer 4. An anode 7 is located a predetermined distance above the gate electrode 6. The anode 7 is formed on the inner surface of a faceplate 8 that forms a vacuum cavity associated with the substrate 1. The faceplate 8 and the substrate 1 are spaced apart from each other by a spacer (not shown), and sealed at the edges. As for color displays, a phosphor screen (not shown) is placed on or near the anode 7.
Since a high-Voltage electrical field is created around micro-UPS in such FEDs, there is the risk of electrical arcing events. Although the cause of electrical arcing is not clearly identified, discharging caused by a sudden large amount of outgassing seems to cause the electrical arcing. According to an experiment result, such arcing occurs with application of an anode voltage as high as 1 kV for both a FED placed within a high-level vacuum chamber without a faceplate, or as a FED vacuum-sealed with a faceplate, as shown in FIG. 1. According to a result of optical microscopy, damage caused by the arcing is mostly detected at the edges of the gate 6a of the gate electrode 6. This is considered to be caused by a strong electric field created near such sharp edges of the gate 6a. An electrical short occurs between the anode 7 and the gate electrode 6 due to the arcing. As a result, a high-anode voltage is applied to the gate electrode 6, thereby damaging the gate insulation layer 4 below the gate electrode 6, and the resistor layer 3 exposed through the well 4a. This damage becomes serious as the anode voltage level increases.
Therefore, the simple configuration of the conventional FED, in which the cathode and anode are spaced apart from each other by just spacers, is not enough to ensure a reliable FED operable with high voltages. The brightness of FED panel depends on the anode voltage level. Thus, a high-brightness FED cannot be manufactured using the conventional FED. The conventional FED cannot focus an electron beam emitted by the micro-tips on the anode, so that it is difficult to achieve a high-resolution display. In addition, a color display with high-color purity cannot be implemented by such a FED.